1. Field of the Invention
This invention relates to a light-emitting device, and in particular, to a light-emitting device having an LED (light-emitting diode) chip where a semiconductor substrate is employed.
2. Description of the Related Art
A light-emitting device comprising a combination of a semiconductor light-emitting element and a fluorescent substance (phosphor) is utilized in various fields as an illumination source, as a backlight source for liquid crystal, etc. A light-emitting device of this kind is manufactured by a process wherein a fluorescent substance is incorporated, at first, in a material for a light-transmitting member such as silicone resin or glass, and the resultant material is then dropped, by using a dispenser, into a recess where a light-emitting element is mounted, the material in the recess being subsequently thermally cured.
In the LED chip where a semiconductor substrate such as a SiC substrate or GaN substrate is employed, the positive electrode and the negative electrode are provided on a top surface and a bottom surface, respectively, of the LED chip. Further, in this LED chip where a semiconductor substrate is employed, a sidewall portion of the substrate is obliquely cut out so as to improve the light extraction efficiency. As a result, it is possible to obtain the emission of light not only from the top surface of the chip but also from the obliquely worked sidewall thereof. In this structure however, part of the chip is exposed without being covered, resulting in the generation of color drift.
Since the fluorescent substance becomes higher in light conversion efficiency as the particle diameter becomes larger, it is desirable to coat the LED chip with a fluorescent layer containing a fluorescent substance of larger diameter at a high concentration. On the occasion of coating the LED chip with a resin containing a fluorescent substance, the resin tends to be attracted by a conductive wire, so that it is impossible to form a fluorescent layer which is uniform in thickness around the LED chip. Further, since a fluorescent substance of larger diameter is more liable to sediment, it is difficult to enable the fluorescent substance to enter below the conductive wire, thus making the density of fluorescent substance non-uniform in the fluorescent layer. A fluorescent layer which is non-uniform in thickness as well as a high density distribution of fluorescent substance would become a cause for generating discoloration.